Density-dependent habitat selection by juvenile Atlantic salmon (Salmo salar) in experimental riverine habitats

1999 ◽  
Vol 56 (7) ◽  
pp. 1298-1306 ◽  
Author(s):  
Tammo P Bult ◽  
Stephen C Riley ◽  
Richard L Haedrich ◽  
R John Gibson ◽  
Jan Heggenes

We investigated habitat use of Atlantic salmon (Salmo salar) parr in experimental riverine enclosures made up of pool, riffle, and run habitats over a range of densities (0.1-1.25 fish·m-2) to test the implicit assumption in habitat modelling that habitat selection does not change with population density. Results indicated that habitat use changed with population density, with relatively more parr in pools and fewer in runs at higher population densities. Temperature influenced parr distribution, with relatively more parr in runs and fewer in riffles and pools at higher temperatures. Parr distribution was primarily affected by hydromorphological differences among pool, riffle, and run habitats. Effects of population density and temperature on use of pool, riffle, and run habitats were often as large as effects of hydromorphological differences among pool, riffle, and run habitats on fish distributions over the range of temperatures and densities observed. Results varied considerably, despite controlled experimental conditions. We concluded that habitat selection by juvenile Atlantic salmon parr may be density dependent and potentially quite variable.

2008 ◽  
Vol 65 (8) ◽  
pp. 1667-1680 ◽  
Author(s):  
A. Jamie F. Gibson ◽  
Heather D. Bowlby ◽  
Peter G. Amiro

We examined relationships between abundance and habitat use in three age classes of juvenile Atlantic salmon ( Salmo salar ) in the Stewiacke River, Nova Scotia, Canada. Using stream gradient as a proxy for habitat quality, we used a double half normal function, modified to include density dependence, to model the relationship between habitat quality and fish density. We found that density was asymmetrically distributed around a similar optimum gradient for all three age classes regardless of abundance. Habitat use was highly density-dependent for age-0 and age-1 juveniles, but not for age-2+ salmon. As abundance of age-0 and age-1 salmon increased, their relative density decreased in low-gradient habitat and increased in higher-gradient habitat, although their absolute density increased in all stream gradient categories. Variation in habitat use was consistent with ideal free theory for age-1 juveniles in high-gradient habitat, but not in low-gradient habitat. Age-2+ individuals appeared not to modify their distribution among habitats, even though increasing competition changes the relative benefit of low-gradient habitat in terms of resource acquisition. In contrast, age-1 individuals responded to increased competition by modifying their distribution along the habitat gradient, even though this may have slightly reduced an individual’s potential for growth.


2010 ◽  
Vol 20 (3) ◽  
pp. 384-392 ◽  
Author(s):  
Pål A. Martinussen ◽  
Grethe Robertsen ◽  
Sigurd Einum

2011 ◽  
Vol 68 (12) ◽  
pp. 2080-2089 ◽  
Author(s):  
Darren M. Ward ◽  
Keith H. Nislow ◽  
Carol L. Folt

Predator effects on prey populations are determined by the number of prey consumed and effects on the traits of surviving prey. Yet the effects of predators on prey traits are rarely evaluated in field studies. We measured the effects of predators on energetic traits (consumption and growth rates) of juvenile Atlantic salmon ( Salmo salar ) in a large-scale field study. Salmon fry were released at 18 sites that encompassed a wide range of predatory slimy sculpin ( Cottus cognatus ) abundance. We sampled salmon after 21 and 140 days to measure salmon growth and estimate consumption using a mass-balance model of methylmercury accumulation. Salmon population density was reduced fivefold at sites with abundant sculpin. Over the early season, salmon consumed less where sculpin were abundant, suggesting that reduced foraging under predation risk contributed to predator-caused mortality. In contrast, over the late season, salmon grew more where sculpin were abundant, suggesting that compensatory growth at reduced salmon population density moderated predator-caused mortality. Predator effects on prey energetics can drive variation in survival and growth, with important consequences for population dynamics.


Ecohydrology ◽  
2020 ◽  
Vol 13 (6) ◽  
Author(s):  
Ross S. Glover ◽  
Chris Soulsby ◽  
Robert J. Fryer ◽  
Christian Birkel ◽  
Iain A. Malcolm

2015 ◽  
Vol 41 (4) ◽  
pp. 1029-1051 ◽  
Author(s):  
Kirsten O. Hannesson ◽  
Elisabeth Ytteborg ◽  
Harald Takle ◽  
Grethe Enersen ◽  
Grete Bæverfjord ◽  
...  

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